John Calvin Commentary Joshua 11:18

"Joshua made war a long time with all those kings." — Joshua 11:18 (ASV)

Joshua made war a long time, etc. Previously, he had, in a short time and, as it were, with the swiftness of running, seized possession of five kingdoms. In the others, the case was different—not from hesitation, weariness, or laziness, but because the Lord exercised His people in various ways, so that He might give a brighter display of His manifold grace, which usually loses its value in our eyes if it is shown only in one and the same way.

Therefore, just as the divine power had previously been strikingly shown by an incredible ease of accomplishment when the enemy was routed in an instant, so a lingering warfare now furnished numerous proofs of heavenly aid. Nor did this happen suddenly and unexpectedly; for God had foretold by Moses that it would be so, so that if the land were immediately converted into a desert, the wild beasts would not become dominant (Deuteronomy 7:22).

In short, we perceive here, as in a mirror, that whatever the Lord had promised by Moses was accomplished in reality, and not by any uncertain event. But while we recognize the certainty of God’s promises, we ought also to meditate on the favor confirmed toward His chosen people, in that He acted as the provident head of a family, not neglecting or omitting anything that was for their benefit.